1. Field of the Invention
The present invention relates to a feeding method of a to-be-transported printing medium for feeding the printing medium in association with an operation for transporting the printing medium to a predetermined printing start position and a printing apparatus.
2. Description of the Related Art
Among image formation apparatuses (printing apparatus) such as a printer, the one has an image formation section such as a printing section that includes a paper feeding apparatus for feeding sheets (printing media) one by one.
The paper feeding apparatus as described above has a structure as shown in FIG. 8A to FIG. 8F for example in which a feeding roller 2 is abutted with the sheet S in a pressurized manner so that the sheet S receives a transportation force. The paper feeding apparatus as described above is also structured such that separation means 7 composed of a separation pad, a separation nail, and a separation bank or the like applies a transportation load to the sheet S so that only the sheet S at the top other than the remaining sheets S at the lower side can be separated. The separated sheet S is sent to a transportation roller 11 by the clockwise rotation of the feeding roller 2 (FIG. 8A to FIG. 8C) and is further transported by both of the feeding roller 2 and the transportation roller 11 (FIG. 8D). When the feeding roller 2 is rotated 360 degrees, then the pressurized contact between the sheet S and the feeding roller 2 is cancelled (FIG. 8E). Thereafter, the sheet S is transported only by the transportation roller 11 to a predetermined printing start position (FIG. 8F).
By the way, in order to reduce the size of an apparatus such as a printing apparatus or to reduce the time required for the sheet S to be fed, it is required to reduce the distance from the feeding roller 2 to a printing head unit (printing section) 13. However, when the distance between them is reduced, some data to be printed may cause a situation in which, when the transportation of the sheet S is performed as shown in FIG. 9A to FIG. 9E, a transportation-completed position PA of the sheet S by the feeding roller 2 comes ahead of the printing start position PB (FIG. 9F). In this case, in order to return the sheet S to the printing start position PB as shown in FIG. 9F, the transportation roller 11 must be rotated in the reverse direction.
Japanese Patent Application Laid-open No. 2002-205838 discloses a paper (sheet) feeding apparatus in which, when the transportation of a sheet is started, a transportation roller in a stoppage status is abutted with the sheet by a feeding roller to subsequently transport the sheet. When a sheet is abutted with the transportation roller in a pressurized manner, a loop is formed. Then, the posture of the sheet is corrected so that the front end of the sheet is parallel to the transportation roller to subsequently transport the sheet to a printing start position by the feeding roller and the transportation roller. Hereinafter, such a paper feeding method will be described as “abutting-type paper feeding”.
Japanese Patent Application Laid-open No. 2002-187634 discloses a method by which, when the front end of a sheet fed by a feeding roller reaches a transportation roller, the transportation roller is already rotated so that the sheet is continuously transported by the transportation roller to the printing start position. Hereinafter, this paper feeding method will be referred to as “no-registration paper feeding (no-position-adjustment paper feeding)”. This “no-registration paper feeding” has an inferior accuracy of a printing start position when compared to that of “abutting-type paper feeding” but can reduce a time required for a paper feeding.
Japanese Patent Application Laid-open No. 2004-082640 discloses “simultaneous control of paper ejection and paper feeding” in which, when a plurality of sheets are subjected to a printing operation, an operation for ejecting an already-printed sheet (current page) and an operation for feeding a sheet to be printed next (next page) are performed simultaneously. When this control is applied to “no-registration paper feeding”, an image is printed on the sheet SA as a current page as shown in FIG. 10A and the printing of the final data to the sheet SA is finished at which the feeding of the sheet SB as a next page is started (FIG. 10B). As a result, an operation for ejecting the sheet SA as a current page and an operation for transporting the sheet SB as a next page to a printing start position can be performed simultaneously (FIG. 10B to FIG. 10G). The result is that the distance between the rear end of the sheet SA as a current page and the front end of the sheet SB can be reduced to improve the rate at which a plurality of pages are printed.
However, when the distance from the paper feeding roller 2 to the printing start position PB at which the printing of the sheet SB as a next page is started is small, “simultaneous control of paper ejection and paper feeding” may cause a problem as described below.
First, as shown in FIG. 11A, an image is printed on the sheet SA as a current page and the printing of the final data to the sheet SA is finished at which the feeding of the sheet SB as a next page is started (FIG. 11B). In this way, an operation for ejecting the sheet SA and an operation for transporting the sheet SB by the feeding roller 2 are performed simultaneously (FIG. 11B to FIG. 11F). In this case, the transportation-completed position PA of the sheet SA by the 360-degree rotation of the feeding roller 2 (FIG. 11F) may come ahead of the printing start position PB (FIG. 11G). In such a case, the transportation roller 11 is rotated in the reverse direction to return the sheet SB to the printing start position PB as shown in FIG. 11G. When this is performed, a risk is caused in which the sheet SA as a current page being ejected is also transported in the reverse direction to cause the rear end of the sheet SA to collide with the transportation roller 11 or the printing section 13 to be bent or damaged.
The risk as described above in which the sheet SA being ejected may be transported by the transportation roller 11 in the reverse direction has been handled by a conventional “simultaneous control of paper ejection and paper feeding” in such a manner in which the feeding roller 2 and the transportation roller 11 are controlled so that the feeding of the sheet SB as a next page can be subjected to an emergency stop. FIG. 13 is a flowchart illustrating the procedure of the control of these rollers 2 and 11.
When a paper ejection instruction for the sheet SA as a current sheet is received (Step S31) and the sheet SB as a next page exists, “simultaneous control of paper ejection and paper feeding” is started (Step S32). First, a transportation motor for rotating the transportation roller 11 receives an instruction for an operation for ejecting the sheet SA as a current page and a paper feeding motor for rotating the feeding roller 2 receives an instruction for rotating the feeding roller 2 360 degrees (Step S33). Next, the reception of a paper feeding instruction is waited (Step S34). Thereafter, the completion of the 360-degree rotation of the feeding roller 2 (Step S35) and the detection by a sheet end section detection sensor (PE sensor) of the existence of a paper (Step S36) are waited. As shown by “1f” of FIG. 11A, the PE sensor detects the front end and the rear end of the sheet by the rotation of the actuator 10 around the axis 10a. This PE sensor 1f detects the existence of a paper (existence of sheet) by the rotation of the lower end of the actuator 10 by the sheet.
When the 360-degree rotation of the feeding roller 2 is completed without the detection by the PE sensor 1f of the existence of a paper, then the absence of paper (absence of sheet) is determined and an error processing is provided to complete the entire processing (Step S37). When the PE sensor 1f detects the existence of a paper, whether the printing start position PB of the sheet SB is fixed or not is determined (Step S38). When the printing start position PB of the sheet SB is not fixed, then an emergency stop instruction is given to the paper feeding motor (Step S39) and the completion of the ejection of the sheet SA by the transportation motor is waited (Step S40). Thereafter, the fixation of the printing start position PB of the sheet SB is waited (Step S41). Then, when the printing start position PB is fixed, the operations of the paper feeding motor and the transportation motor are newly started (Step S42). Then, the processing proceeds to Step S47 (which will be described later).
On the other hand, when Step S38 already fixes the printing start position PB, based on the relation between degrees required for the feeding roller 2 to be rotated in order to complete a 360-degree rotation and the printing start position PB, whether the transportation roller 11 needs to be rotated in the reverse direction or not is determined (Step S43). Specifically, the transportation-completed position PA of the sheet SB when the 360-degree rotation of the feeding roller 2 is completed is estimated so that, when the transportation-completed position PA comes ahead of the printing start position PB as shown in FIG. 11F, it is determined that the reverse rotation of the transportation roller 11 for returning the front end of the sheet SB to the printing start position PB as shown in FIG. 11G is required. On the other hand, when the transportation-completed position PA does not come ahead of the printing start position PB, it is determined that the reverse rotation of the transportation roller 11 is not required.
When it is determined that the reverse rotation of the transportation roller 11 is required, an emergency stop instruction is given to the paper feeding motor (Step S44) and the feeding of the sheet SB is stopped. Then, the completion of the ejection of the sheet SA by the transportation motor is waited (Step S45). Thereafter, the operations of the paper feeding motor and the transportation motor are newly started (Step S46) and the processing proceeds to Step S47 (which will be described later). On the other hand, when Step S43 determines that the reverse rotation of the transportation roller 11 is not required, then the processing directly proceeds to Step S47.
In Step S47, the 360-degree rotation of the feeding roller 2 is completed and then the forward or reverse rotation of the transportation roller 11 causes the sheet SB to be transported to the printing start position PB, thereby completing the processing.
In “simultaneous control of paper ejection and paper feeding” as described above, the paper feeding motor is controlled by the procedure shown in the flowchart of FIG. 14. This processing is performed by an interrupt by a cycle timer.
When an instruction for the operation of the paper feeding motor is received, then the paper feeding motor is firstly acceleration-controlled until the acceleration of the feeding roller 2 is completed (Steps S51 and S52). When the acceleration is completed, the feeding roller 2 is constant speed-controlled (Step S53). The constant speed control is continued until an emergency stop instruction is received or the 360-degree rotation of the feeding roller 2 is obtained (Steps S54 and S55). After the constant speed control, the feeding roller 2 is deceleration-controlled until the deceleration of the feeding roller 2 is completed (Steps S56 and S57).
FIG. 12A to FIG. 12I illustrate an operation for a case in “simultaneous control of paper ejection and paper feeding” as described above in which the printing start position PB of the sheet SB comes ahead of the transportation-completed position PA.
First, in accordance with a timing at which the printing of the final data to the sheet SA as a current page is completed, an operation for ejecting the sheet SA and an operation for feeding the sheet SB as a next page are simultaneously started as shown in FIG. 12A and FIG. 12B (Step S33). The sheet SB is fed as shown in FIG. 12C and the front end is detected by the PE sensor if as shown in FIG. 12D. In the case of this example, the printing start position PB is already fixed when the existence of a paper is detected by the PE sensor 1f and it is estimated that the transportation-completed position PA comes ahead of the printing start position PB. Thus, it is determined that the reverse rotation of the transportation roller 11 is required. Thus, the processing proceeds from Step S36 to Steps S38, S43, and S44 and an emergency stop instruction is given to the paper feeding motor. As a result, the processing proceeds from Step S54 to Step S56 in FIG. 14 and the paper feeding motor is deceleration-controlled and the feeding roller 2 is stopped as shown in FIG. 12E.
Thereafter, the completion of the operation for ejecting the sheet SA is waited. Then, Step S46 starts the operations of the paper feeding motor and the transportation motor again and the feeding roller 2 and the transportation roller 11 are rotated as shown in FIG. 12F and FIG. 12G. Then, Step S47 transports the sheet SB to the transportation-completed position PA by the 360-degree rotation of the feeding roller 2 as shown in FIG. 12H. Thereafter, the reverse rotation of the transportation roller 11 causes the sheet SB to reach the printing start position PB as shown in FIG. 12I.
When the reverse rotation of the transportation roller 11 is required in the “simultaneous control of paper ejection and paper feeding” as described above, the feeding of the sheet SB as a next page is temporarily stopped and the feeding of the sheet SB as a next page is not started until the ejection of the sheet SA as a current page is completed. Although this control causes the reduction of the printing speed, the problem due to the transportation of the sheet SA as a current page in the reverse direction can be avoided.
FIG. 15 illustrates the rotation position and speed change of the feeding roller 2 in the “simultaneous control of paper ejection and paper feeding” as described above.
When the driving of the paper feeding motor is started to rotate the feeding roller 2, one sheet SB is separated and fed and the front end of the sheet SB reaches the PE sensor 1f at which the time t1 is reached and the feeding roller 2 is at the rotation position “p1”. These “p1” and “t1” change depending on the behavior of the sheet SB. At the time t1, the determination by Step S38 is provided. When the printing start position PB is not fixed until the time t1, Step S39 provides an emergency stop instruction for the paper feeding motor. As a result, the paper feeding motor is deceleration-controlled after the time t1 and is stopped at the position P2. The rotation position and speed of the feeding roller 2 change so as to draw the trajectory as shown by the broken line in FIG. 15. When the feeding roller 2 is stopped at the emergency stop position P2, the front end of the sheet SB is stopped at a position at which the sheet SB is not transported by the transportation roller 11 (i.e., a position sufficiently far away from the position p3 at which the sheet SB is caught by the transportation roller 11). The PE sensor 1f is provided in order to set the emergency stop position P2 so as to satisfy the conditions as described above.
When the printing start position PB is fixed in Step S38 and the next Step S43 determines that the reverse rotation of the transportation roller 11 is required, then Step S44 issues an emergency stop instruction to the paper feeding motor. Thus, the rotation position and speed of the feeding roller 2 change so as to draw the trajectory as shown by the broken line in FIG. 15.
When Step 43 determines that the reverse rotation of the transportation roller 2 is not required, then the feeding roller 2 is driven until the paper feeding is completed. Thus, the rotation position and speed of the feeding roller 2 change so as to draw the trajectory as shown by the solid line in FIG. 15.
However, in the “simultaneous control of paper ejection and paper feeding” of the conventional example, there may be a case in which an increased rotation speed of the feeding roller 2 for providing a high-speed printing causes the time t1 at which the detection by the PE sensor is provided to be earlier. As a result, it occurs more times that the processing of to-be-printed data cannot be completed until the time t1 and the printing start position is not fixed. In this case, a problem is caused in which the printing speed is reduced in spite of the increased rotation speed because the feeding roller 2 is frequently subjected to an emergency stop.